1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display that is capable of emphasizing brightness in a specified area of a liquid crystal display panel and a driving method for emphasizing brightness in a specified area of a liquid crystal display panel.
2. Description of the Related Art
Generally, liquid crystal displays have the advantages of small size, light weight, thin profile and low power consumption. Accordingly, liquid crystal displays are used for notebook PCs, office automation equipment, audio/video equipment and other visual type equipment. In particular, an active matrix liquid crystal display panel is a liquid crystal display panel suitable for displaying motion picture. A thin film transistor (hereinafter, referred to as TFT) is used as a switching device in each pixel of an active matrix liquid crystal display panel.
FIG. 1 is a block diagram representing a liquid crystal display of the related art. As shown in FIG. 1, the related art liquid crystal display includes a Liquid Crystal Display (LCD) panel 6, a data driver 8 to supply data to data lines DL1 to DLn, a gate driver 10 to supply scan pulses to the gate line GL1 to GLm of the liquid crystal display panel 6, a timing controller 4 to control the data driver 8 and the gate driver 10, an interface part 2 to supply digital video data DATA and an H synchronization signal and a V synchronization signal. A computer system 12 supplies the digital video data to the interface part 2 of the liquid crystal display.
As discussed above, the computer system 12 is formed separately from the liquid crystal display. A graphic card (not shown) installed in the computer system 12 converts pixel data and synchronization signals inputted from the outside to be suitable for the resolution of the liquid crystal display panel 6. The graphic card then supplies the converted data and signals to the interface part 2 of the liquid crystal display.
Although not shown in FIG. 1, the interface part 2 of the liquid crystal display receives synchronization signals, such as data RGB DATA, input clocks DCLK, horizontal synchronization signals H, vertical synchronization signals V, data enable signals DE, etc., inputted from the computer system 12 such that the signals are inputted into the timing controller 4. A Low Voltage Differential Signal (LVDS) interface and a Transistor-Transistor Logic (TTL) interface are mainly used for transmitting the data and the synchronization signals from a drive system. Further, interface functions are integrated into one chip along with the timing controller 4.
The timing controller 4 generates gate control signals GDC using the synchronization signals from the interface part 2 to control the gate driver 10. Further, the timing controller 4 generates data control signals DDC to control the data driver 8 using the synchronization signals from the interface part 2. The timing controller 4 aligns the data from the interface part 2 to supply the aligned data to the data driver 8.
The gate driver 10 includes a shift register to sequentially generate scan pulses, such as gate high pulses, in response to the gate drive control signal GDC supplied from the timing controller 4. The gate driver 10 also includes a level shifter to shift the voltage of the scan pulses to an appropriate level suitable for driving liquid crystal cells Clc. Video data through the data line DL are supplied to the pixel electrode of the liquid crystal cell Clc by a TFT in response to the scan pulses.
The data driver 8 receives the data drive control signals DDC from the timing controller 4 together with red R, green G and blue B video data. The data driver 8 latches the red R, green G and blue B digital video data in synchronization with the data drive control signals DDC, and then corrects the latched data in accordance with the gamma voltage Vγ generated from a gamma voltage generator (not shown). Then, the data driver 8 converts the corrected data into analog data to supply the converted data to the LCD panel by data lines DLn in a line-by-line fashion.
The liquid crystal display panel 6 has liquid crystal injected between two glass substrates, and the data lines DL1 to DLn and gate lines GL1 to GLm are formed to cross each other on the lower glass substrate thereof. A TFT formed at the intersection of the data lines DL1 to DLn and the gate lines GL1 to GLm switches the data from the data lines DLI to DLn to the liquid crystal cell Clc in response to scan pulses. To this end, the gate terminal of the TFT is connected to the gate line GL1 to GLm, the source terminal is connected to the data line DL1 to DLn, and the drain terminal is connected to a pixel electrode of the liquid crystal cell Clc.
The liquid crystal cell is a passive luminous device and controls the transmittance of the light supplied from a same backlight unit. A group of liquid crystal cells in a liquid crystal display panel are used to display a picture. The liquid crystal display panel has been intensively developed to increase brightness such that the average brightness of the liquid crystal display panel is far above the average brightness level of 100 nit of the Cathode Ray Tube (CRT). Thus, the liquid crystal display panel can make users feel tired because the display is too bright. This is because the liquid crystal display panel is unilaterally set to a high brightness corresponding to the display of a motion picture, a TV video or a high-resolution picture, which can require a brightness level greater than 300 nit. In other words, since the liquid crystal display panel has a high preset average brightness level to accommodate a high-resolution picture or moving video image, the LCD panel is too bright for still and/or low-resolution images, which can make users feel tired.
FIG. 2 is a diagram representing a high picture quality mode and a word mode simultaneously displayed on a related art liquid crystal display panel shown in FIG. 1. As shown in FIG. 2, 100˜150 nit brightness level class is suitable to the user for the average brightness of a first mode area A, such as a word processing mode. A 300˜400 nit brightness level class is suitable for the average brightness of a second mode area B, such as a TV video, motion picture or high quality picture mode. However, the brightness of the LCD panel used for a monitor is normally set to a 200˜300 nit brightness level on average. Due to the 200˜300 nit average brightness level typical used, there is a problem in that area A of the LCD panel is too bright for the first mode and area B of the LCD panel is too dark for the second mode.
The brightness level of an LCD panel can be controlled by adjusting a lamp drive frequency through an On-Screen Display (OSD) or by adjusting the gamma voltage inputted to the data driver. However, it is impossible to control the brightness level of the LCD panel in just a portion or a specified area of an LCD panel since the entire LCD panel receives light from the same backlight unit. In other words, it is impossible to have a first mode area having a brightness level of 100˜150 nit together at the same time with a second mode area having a brightness level of 300˜400 nit in a liquid crystal display panel of the related art.